My former dentist's office would send an appointment reminder via text message with the instruction to reply with a 'yes' or 'no.'

We got a notice in the mail that they were no longer accepting our insurance, so when the confirming text message arrived, I texted back 'no.'

The day of the appointment I got a phone call from a very snippy office person inquiring as to why I had not come to the appointment. When I explained the insurance issue and that I had replied 'no' to their text, she said, "We don't read those!"